Method of recovering tin.



WILLIAM HOSKINS, OF CHICAGO, ILLINOIS.

METHOD OF RECOVERING TIN.

Specification of Letters Patent.

Patented Feb. 24, 1914:.

Application filed April 10, 1%)18. Serial No. 760,124.

To alt ro/1.0m it may concern Be 1t known that I, WILLIAM HosKms, a

citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Methods of Recovering Tin, of which the following is a specification.

My invention relates to an improved method of producing commercial tin from more or less oxidized tin or tin alloys.

In the process of winning tin from tlll plate scrap, for example, a product is obtained consisting of a mixture of finely divided tin and tin oxid, which has always been difficult heretofore to convert'into commercial tin, and one of my objects is to provide' a simple and improved method of economically treating said product. My" improved method may. also be employed to advantage in the production of commercial tin from drosses produced in the manufacture of tin-plate, and from type-metal, both of which contain tin or tin alloy and oxid thereof.

For the practice of my improved method I provide a furnace having an upright chamber equipped with twyers at different levels,

the twyers having valves whereby the air dotted line-14. with charcoal which is ignited supply at each of said 'levels may be regu lated. I charge the furnace with carbon to a level above the upper twyers and bymeans of the valves the volume of air forced in at 'each of thetwyer levels is so regulated asto maintain the mass of carbon incandescent throughout, but temperatures increaslng with the height of the level. The metal oxid or mixture'of themetal and its oxid is fed into the top of the furnace and subjected to the action of the upper hottest zone in'a reducing atmosphere which quickly reduces the highly refractory oxid of tin to metal and melts the metal causing it to run down through the lowerzones. The said lower zones also contain a reducing atmosphere, but of diminishing temperatures which serve to maintain the metal in molten condition without danger of reoxidation.

The molten metal is I allowed .to escape through an opening in the lower end of the furnace wall where it is collected in a suitable basin or float.

In the accompanying drawing which illustrates a furnace suitable for carrying out .2 in Fig. 1.

my improved method Figure 1 is a vertical section of the furnace taken on line 1 in Fig. 2; and Fig. 2 is a plan section taken on line The vertical walls 3 of the furnace are of fire-brick inclosing an upright chamber 4. At the lower end of the chamber is an iron base-plate 5 having a slight inclination, and

above the lower end thereof is an outlet' "opening 6 1n the furnace wall. Below the opening 6 is a basin or float 7 The furnace illustrated is equipped with three sets of twyers of which the twyers 8 form the upper set, the twyers 9 an intermediate set andthe twyers 10 the lower set. They'extend into the chamber 4 from three sides as indicated and each of the twyers is provided with a hand-operated valve 11 for regulatmg the supply of air therethrough. The twyers communicate with a bustle pipe 12 which receives air under pressure from a compressor or a compressed air supplier, not shown. Surmount-i-ng the chamber 4 is a; hook and stack 12 for the-escape of gases, leaving an opening 13 below the hood through which the chamber may be charged.

In practice the chamber is filled to approximately the level indicated by the and maintained incandescent by the air forced in at the twyers. The valves 11 of the lower twyers 10 are opened only far enough to .permit a comparatively small quantity-of air to pass therethrough to sup-.

port combustion of the charcoal in the lower zone adjacent to the twyers 10 causing the twyers 8 are opened still wider to effect still more rapid combustion of the carbon in the zone adjacent to the twyers 8. Thus the temperature is greatest in the upper part of the furnace chamber and diminishes towardthe lower end thereof, while a reducing atmosphere 1s maintained throughout the, chamber. The tin or tin alloy and oxids thereof are shoveled into the chamber 4 through the opening 13 and are subjected in the upper zone to a melting temperature in a reducing atmosphere which efl'ects quick deoxidation of the metal oxids and melts the metal. lates downward through the incandescent mass in the .zones 9 and 10 which maintains the metal in a molten state and against reoxidation. As the molten metal descends to the base plate 5 it flows out through the opening 6 into the float 7. Any-unconsumed charcoal and unreduced oxids escaping from the chamber into the float may be skimmed off and returned to the furnace. As metallic impurities in the tin as a rule are heavier than tin, they descend to the bottom of the float 7, leaving the tin in a commercially pure condition overlying the impurities; It becomes an easy matter therefore to ladle the tin out of the float into molds to form ingots of commercially pure tin. f

The valves 11 make it possible to suitably control the temperatures at the different zones. The upper zone should in practice be maintained at a temperature which, while exceeding the melting point of tin, will not effect volatilization thereof and consequent loss by escape through the stack. The heat of the lower zone should be below that of the upper zone and so controlled that the molten tin will run out into the float at a temperature neither too high nor too low,

otherwise it is apt to be brittle and have itscolor and luster impaired. By manipulating the valves 11 the operator may so regulate the temperature as to obtain the best results and maintain an output of uniformly high grade.

The latter as it is melted perco-' 'phere of a temperature lower than that first named.

2. The herein described method of treating a mixture of tin, or tin alloys, and-their oxids, which consists in subjecting the same in a reducing atmosphere to a temperature ,exceeding the fusing point of tin, to reduce the oxids and melt the metal, then passing the molten metal downward through, zones of reducing atmosphere of progressively decreasing temperatures.

3. The herein described method of treating a mixture of tin, or tin alloys, and-their oxids, which'consists in maintaining incandescent abed of carbon by introducing air into, the same at different levels and in progressively decreasing quantities in the downward direction, introducing the mixture to be treated upon the top of the bed,reduc1ng the oxids and melting the metal and causing.

it to percolate through the progressively decreasing'heat zones in the bed, and discharging the molten product from the base of the bed.

s WILLIAM HOSKINS. In presence of.-

DAISY G. THORSEN, OT'rILm O. Avrsus. 

